Porous metals are useful because they are catalytically active and highly electrically conductive. Porous metal films are useful in, for example, transistors, solar cells, and electrochemical sensors. Among the metallic porous films, gold films are chemically stable and have a unique surface chemistry. Porous gold films have the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to prepare porous gold films, such as, de-alloying, templating, electrochemical, and self-assembling. Rigid template-directed methods for forming porous gold films typically achieve a uniform pore-size distribution, but the electrocatalytic and sensing performance of such films is insufficient due to limited porosity. Furthermore, post-dissolution of the rigid template during production is very time-consuming. There is a need for a simple, economical and environmentally-friendly approach to effectively prepare three-dimensional porous gold films with high surface area-to-volume ratios, high conductivity, and good mechanical properties.
A potential method is by the deposition of nanoparticles (NPs) on the surface of carbon nanotubes. The most widely studied approaches include: electrodeposition (ED) (for example, Zeng et al. Analyst, 2010, 135, 1726-30 and Siqueira, Jr. et al. Phys. Chem. Chem. Phys., 2012, 14, 14340-43); electrolytic deposition (for example, Choi et al. J. Am. Chem. Soc., 2002, 124 (31), 9058-59); electroless deposition (for example, Qu et al. J. Am. Chem. Soc., 2005, 127 (31), 10806-7); and physical methods including sputtering (for example, Soin et al. Diamond and Related Materials, 2010, 19, (5-6), 595-8), thermal evaporation (for example, Gingery et al. Carbon, 2008, 46, (14), 1966-72), electron beam evaporation (for example, Star et al. J. Phys. Chem. B, 2006, 110 (42), 21014-20, Eder Chem. Rev., 2010, 110 (3), 1348-85); and dispersion of NPs obtained with chemical methods onto functionalized CNTs (for example Hsu et al. RSC Adv., 2014, 4, 14777-80).